Vulcanizable rubber composition

ABSTRACT

A vulcanizable rubber composition composed of 100 parts by weight of a terpolymer rubber (A) composed of 35 to 80 mole % of epichlorohydrin, 15 to 50 mole % of ethylene oxide and 5 to 15 mole % of an unsaturated epoxide, 0.2 to 10 parts by weight of a non-sulfur vulcanizing agent, and 0 to 10 parts by weight of a vulcanization aid. A vulcanized rubber prepared from this composition has superior sour gasoline resistance (softening resistance and resistance to embrittlement) and cold resistance. A rubber mixture (B) of an epichlorohydrin-ethylene oxide copolymer rubber and an epichlorohydrin-unsaturated epoxide copolymer rubber containing 35 to 80 mole % of epichlorohydrin, 15 to 50 mole % of ethylene oxide and 5 to 15 mole % of an unsaturated epoxide may be substituted for the terpolymer rubber (A).

This is a division of patent application Ser. No. 927,620, filed July24, 1978 now U.S. Pat. No. 4,268,644.

This invention relates to a vulcanizable rubber composition to be usedin applications involving contact with sour gasoline.

In recent years, control measures against automobile exhaust gases havebeen taken to meet the social need for improving the atmosphericenvironment, and efforts have been made to improve automobile engines.As a result, a number of important safety parts made of syntheticrubbers which meet the requirement of thermal stability, gasoline (oroil) resistance and cold resistance at the same time have been mountedon automobiles. Among the existing synthetic rubbers, anepichlorohydrin-ethylene oxide copolymer rubber (sometimes to bereferred to as CHC hereinbelow) has a particularly well balancedcombination of these properties and therefore, has found extensive useas hoses, gaskets, O-rings and oil seals.

On the other hand, as a result of engine improvement, the ambientatmosphere of an engine tends to be at a higher temperature thanheretofore. This renders gasoline susceptible to oxidation and resultsin the formation of sour gasoline. The sour gasoline is caused by theoxidation of highly unsaturated ingredients of gasoline to peroxides byoxygen in the air, which peroxides further undergo oxidation to aldehydecompounds or carboxylic acids. Recognizing the serious effect of sourgasoline, General Motors Corporation already established a testingmethod [GM OP-9308 (1966)] to exert a proper control over it.

CHC has superior gasoline resistance, but on contact with sour gasoline,is easily softened and dissolved. Thus, automotive parts made of CHCcannot retain their shape, and therefore, it may possibly lead to aserious accident. This phenomenon is ascribable to the fact that theperoxides in the sour gasoline attack the ether linkage that forms themain chain of CHC, and induces the breakage of the main chain of CHC.[The breakdown of the ether linkage by auto-oxidation is described indetail in Angew. Markromol. Chem. 16/17, 103, (1971).]

One conceivable method for removing the aforesaid defect of CHC is toblend CHC with an acrylonitrile/butadiene copolymer rubber or an acrylicrubber. The blend of CHC with the acrylonitrile-butadiene copolymerrubber apparently does not soften nor dissolve on contact with sourgasoline. However, because of the poor compatibility between the twocomponents and the markedly low break elongation, this blended rubbercannot endure practical application. The blend of CHC and acrylic rubbercannot be prevented from softening and dissolving by sour gasolinebecause the acrylic rubber essentially has poor resistance to gasoline.

It is an object of this invention therefore to provide a vulcanizablerubber composition which can be free from softening and dissolving bysour gasoline without sacrificing the thermal stability, gasoline (oroil) resistance and cold resistance of CHC, and thus can be used inapplications involving contact with sour gasoline.

According to this invention, this object can be achieved by avulcanizable rubber composition comprising

(1) 100 parts by weight of a rubber selected from the group consistingof (A) a terpolymer rubber composed of 35 to 80 mole% ofepichlorohydrin, 15 to 50 mole% of ethylene oxide and 5 to 15 mole% ofan unsaturated epoxide, and (B) a rubber mixture prepared by mixing anepichlorohydrin-ethylene oxide copolymer rubber with anepichlorohydrin-unsaturated epoxide copolymer rubber so that the mixturewill contain 35 to 80 mole% of epichlorohydrin, 15 to 50 mole% ofethylene oxide and 5 to 15 mole% of an unsaturated epoxide;

(2) 0.2 to 10 parts by weight of a non-sulfur vulcanizing agent; and

(3) 0 to 10 parts by weight of a vulcanization aid.

One characteristic feature of the present invention is the use of anunsaturated epoxide as a comonomer constituting the terpolymer rubber(A) or the rubber mixture (B), and a non-sulfur vulcanizing agent whichdoes not cause the unsaturated bond of the unsaturated epoxide to beinvolved in vulcanization. A vulcanized rubber prepared from thecomposition of this invention posseses the unsaturated bond of theunsaturated epoxide as a result of being vulcanized with the non-sulfurvulcanizing agent. Accordingly, even if the peroxide in sour gasolinecauses the breakage of the ether linkage of the main chain of thevulcanized rubber, the peroxide simultaneously reacts with theunsaturated bond of the unsaturated epoxide in the vulcanized rubber toinduce vulcanization, and therefore, the softening and dissolving of thevulcanized rubber is prevented.

The terpolymer rubber (A) should be composed of 35 to 80 mole%(preferably 48 to 74 mole%) of epichlorohydrin, 15 to 50 mole%(preferably 20 to 40 mole%) of ethylene oxide and 5 to 15 mole%(preferably 6 to 12 mole%) of an unsaturated epoxide. The rubber mixture(B) is obtained by mixing an epichlorohydrin-ethylene oxide copolymerrubber with an epichlorohydrin-unsaturated epoxide copolymer rubber sothat the resulting mixture may contain 35 to 80 mole% (preferably 48 to74 mole%) of epichlorohydrin, 15 to 50 mole% (preferably 20 to 40 mole%)of ethylene oxide and 5 to 15 mole% (preferably 6 to 12 mole%) of anunsaturated epoxide. In either the terpolymer rubber (A) or the rubbermixture (B), if the content of ethylene oxide is less than 15 mole%, thegasoline (oil) resistance is degraded. If the content of the unsaturatedepoxide is less than 5 mole%, no effect of preventing softening of thevulcanized rubber in sour gasoline is obtained, and if it exceeds 15mole%, hardening deterioration is caused by the effect of sour gasoline,and the vulcanized rubber loses rubbery elasticity and becomes brittle.

The epichlorohydrin-ethylene oxide copolymer rubber used as onecomponent of the rubber mixture (B) is preferably obtained bycopolymerizing 30 to 70 mole% of epichlorohydrin with 70 to 30 mole% ofethylene oxide. Such a rubber is sold under the trademark Hydrin 200 andHerclor C by B. F. Goodrich Chemical Co. and Hercules Incorporated,respectively. As the epichlorohydrin-unsaturated epoxide copolymer, theother component of the rubber mixture (B), a copolymer composed of 80 to90 mole% of epichlorohydrin and 20 to 10 mole% of an unsaturated epoxideis preferred.

Examples of the unsaturated epoxide are allyl glycidyl ether, glycidylmethacrylate, glycidyl acrylate and butadiene monooxide.

The terpolymer rubber (A), the epichlorohydrin-ethylene oxide copolymerrubber and the epichlorohydrin-unsaturated epoxide copolymer rubber canbe prepared in accordance with ordinary solution-polymerization recipes.All of them preferably have a Mooney viscosity [ML₁₊₄ (100° C.)] of 10to 150.

When a rubber having an unsaturated epoxide as a copolymer component isto be vulcanized, a sulfur-type vulcanizing agent is usually employed toinduce crosslinking by utilizing its unsaturated bond. However, when asulfur-type vulcanizing agent is used to vulcanize the rubbercomposition of this invention, the vulcanized rubber has a decreasedcontent of the unsaturated bond and a poor resistance to sour gasoline,and the object of this invention cannot be achieved. It is necessarytherefore to use a non-sulfur vulcanizing agent, that is a vulcanizingagent of the type which induces a vulcanization reaction through achlorine atom, in order to leave the unsaturated bond of the unsturatedepoxide in the vulcanized rubber. Vulcanizing agents of this type aregenerally used for the vulcanization of saturated epichlorohydrinrubbers, and typical examples include (1) a vulcanizing agent selectedfrom 2-mercaptoimidazolines and 2-mercaptopyrimidines, and (2) avulcanizing agent selected from trithiocyanuric acid and its derivatives(U.S. Pat. No. 3,787,376). When the vulcanizing agent (1) is used, ametal compound selected from the aromatic carboxylic acid salts,saturated aliphatic carboxylic acid salts, carbonates, phosphites,silicates and oxides of metals of Groups IIA, IIB and IVA of theperiodic table is usually employed as a vulcanization aid (U.S. Pat. No.3,341,491). In the case of using the vulcanizing agent (2), too, the useof the above metal compounds as a vulcanization aid is preferred.Especially preferred vulcanizing agent systems include a combination of2-mercaptoimidazoline and red lead, a combination of trithiocyanuricacid and magnesium oxide, and a combination of trithiocyanuric acid,magnesium oxide and calcium carbonate. The amount of the vulcanizingagent is 0.2 to 10 parts by weight, preferably 0.5 to 3 parts by weight,per 100 parts by weight of the terpolymer (A) or the rubber mixture (B).The amount of the metal compound as vulcanization aid is up to 10 partsby weight, preferably 2 to 7 parts by weight on the same basis.

The rubber composition of this invention is prepared by mixing theterpolymer (A) composed of epichlorohydrin, ethylene oxide andunsaturated epoxide or the rubber mixture (B) composed of theepichlorohydrin-ethylene oxide copolymer rubber and theepichlorohydrin-unsaturated epoxide copolymer rubber with thesulfur-free vulcanizing agent and ordinary rubber compounding agentssuch as a vulcanization aid, a reinforcing agent, a filler, aplasticizer or an antioxidant by an ordinary mixer such as a roll millor a Banbury mixer.

Heating the rubber composition at 120° to 200° C. for 5 to 120 minutesgives a rubber vulcanizate having superior resistance to sour gasoline.

To improve the properties, especially compression set, of thisvulcanizate, it is preferably heat-treated at 100 to 180° C. for 1 to 24hours. The resulting vulcanizate is suitably used in applicationsinvolving contact with sour gasolines, for example in fuel system hoses,diaphragms and packings attached to internal combustion engines ofautomobiles, air planes, agricultural machinery, and the like.

The following Examples are given to illustrate the present inventionmore specifically.

The sour gasoline resistance and cold resistance in these examples weremeasured by the following methods.

Resistance to sour gasoline

(1) Resistance to softening

A sour gasoline having a peroxide value (measured by UOP Testing Method33-59 of Universal Oil Products Company) of 6.1 gram-equivalents/1000liters was prepared by exposing "Nisseki High Arom 2S" (a commerciallyavailable standard test gasoline) intermittently to the irradiation ofultraviolet rays for 2 weeks.

A vulcanized rubber specimen, 15 mm in length, 10 mm in width and 0.5 mmin thickness, was dipped in the sour gasoline, and allowed to stand for240 hours in an atmosphere at 60° C. Immediately then, the pencilscratch value of the surface of the speciment was measured by a methodsubstantially in accordance with the pencil scratch test method of ASTMD 3363. The resulting values were rated on a scale of A, B, C and D.Specimens having softening resistance with ratings of A and B wereregarded as acceptable. The ratings of the pencil scratch values areshown in Table 1.

                  TABLE 1                                                         ______________________________________                                                Pencil scratch                                                                            Surface condition of the                                  Rating  value       vulcanizate                                               ______________________________________                                        D       5B-6B       The surface is markedly softened,                                             and susceptible to disintegration                         C        B-4B       The surface is softened, and is                                               liable to be tacky.                                       B       4H-HB       The surface is slightly softened,                                             but no appreciable change is                                                  noted on the surface.                                     A       4H or harder                                                                              No change occurs on the surface.                          ______________________________________                                    

(2) Resistance to embrittlement

A vulcanized rubber which has undergone hardening deterioration by sourgasoline is found to be acceptable by the softening resistance test, butcannot be used in practical application because it loses rubberyelasticity and is brittle. To check such a vulcanized rubber, vulcanizedrubber specimens evaluated as ratings A and B in the above softeningresistance test are bent by an angle of 180° immediately after thesoftening resistance test, and after standing in this state for 10seconds, the specimens are observed for the occurrence of cracks at thebent area. The specimen in which cracks occur is judged to be inferiorin resistance to embrittlement.

Cold resistance

In accordance with the low temperature impact embrittlement testingmethod of ASTM A 746, the breakage of a vulcanized rubber specimen at-35° C. was tested.

EXAMPLE 1

An epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer rubberprepared by a known solution-polymerization method using anorganoaluminum compound catalyst was mixed with compounding agents inaccordance with the compounding recipe shown in Table 2 by a cold roll.The mixture was heated at 155° for 30 minutes under pressure, andheat-treated at 150° C. for 4 hours to afford a vulcanizate.

                  TABLE 2                                                         ______________________________________                                        Epichlorohydrin-ethylene oxide-                                                                   100     parts by weight                                   unsaturated epoxide terpolymer                                                Stearic acid        1                                                         FEF carbon black    40                                                        Red lead            7                                                         2-Mercaptoimidazoline                                                                             1.2                                                       Nickel dibutyldithiocarbamate                                                                     1                                                         ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                                  Run No.                                                                       1   2     3       4     5     6                                               Com-                  Com-                                                    parison                                                                             Invention       parison                                       ______________________________________                                        Terpolymer rubber                                                             composition                                                                   (mole %)                                                                      Epichlorohydrin                                                                           50    50    50    50    50    50                                  Ethylene oxide                                                                            50    47    45    40    35    30                                  Allyl glycidyl                                                                            --     3     5    10    15    20                                  ether                                                                         Sour gasoline                                                                 resistance                                                                    (1) Softening                                                                             D     C     B     A     A     A                                   resistance                                                                    (2) Resistance to                                                                         --    --    No    No    No    Crack                               embritlement            crack crack crack occurred                            Cold resistance                                                                           No breakage occurred                                              ______________________________________                                    

It is seen from Table 3 that the epichlorohydrin-ethylene oxidecopolymer rubber easily softens and disintegrates in sour gasoline, buta copolymer obtained by further copolymerizing allyl gylycidyl ethershows superior resistance to sour gasoline. This effect is not obtained,however, if the ratio of the allyl glycidyl ether is less than 5 mole%.

If its ratio is 20 mole%, the sour gasoline resistance is satisfactory,but the vulcanized rubber loses rubbery elasticity and developscrackings in the cold resistance test, thus failing to serve forpractical purposes.

EXAMPLE 2

The same test as in Example 1 was performed using anepichlorohydrin-ethylene oxide-unsaturated epoxy terpolymer with a fixedproportion of the unsaturated epoxide. The results are shown in Table 4.

                                      TABLE 4                                     __________________________________________________________________________               Run No.                                                                       7    8   9   10  11  12                                                       Compari-             Compari-                                                 son  Invention       son                                           __________________________________________________________________________    Terpolymer rubber                                                             composition (mole %)                                                          Epichlorohydrin                                                                          35   40  50  60  70  80                                            Ethylene oxide                                                                           55   50  40  30  20  10                                            Allyl glycidyl                                                                           10   10  10  10  10  10                                            ether                                                                         Sour gasoline                                                                 resistance                                                                    (1) Softening                                                                            D    B   A   A   A   A                                             resistance                                                                    (2) Resistance to                                                                        --   No  No  No  No  No                                            embrittlement   crack                                                                             crack                                                                             crack                                                                             crack                                                                             crack                                         Cold resistance                                                                          No breakage occurred Broken                                        __________________________________________________________________________

It is seen from Table 4 that the properties of the terpolymer rubbervary depending upon the proportion of ethylene oxide. In other words,when the proportion of ethylene oxide exceeds 50 mole%, the rubber hasinferior resistance to gasoline (the pencil scratch hardness decreasesextremely), and if it is less than 15 mole%, the rubber has poor coldresistance.

EXAMPLE 3

Each of epichlorohydrin-ethylene oxide-unsaturated epoxide terpolymerrubbers having the compositions shown in Table 5 was tested in the sameway as in Example 1. The results are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                                 Run No.                                                                       13   14     15      16    17    18                                                    In-                 In-                                               Comparison                                                                            vention Comparison  vention                                  ______________________________________                                        Terpolymer                                                                    rubber com-                                                                   position                                                                      (mole %)                                                                      Epichlorohydrin                                                                          30     25     45    85    75    80                                 Ethylene oxide                                                                           55     55     50    10    10    15                                 Allyl glycidyl                                                                           15     20      5     5    15     5                                 ether                                                                         Resistance to                                                                 sour gasoline                                                                 (1) Softening                                                                            D      D      B     A     A     A                                  resistance                                                                    (2) Resistance                                                                           --     --     No    No    No    No                                 to embrit-               crack-                                                                              crack-                                                                              crack-                                                                              crack-                             tlement                  ing   ing   ing   ing                                                                       No                                     Cold resistance                                                                          No breakage   Broken  Broken                                                                              break-                                                                        age                                    ______________________________________                                    

The results demonstrate that when the proportion of the ethylene oxideunit exceeds 50 mole%, the sour gasoline resistance of the terpolymerrubber cannot be improved even if the proportion of the unsaturatedepoxide is increased. It is also clear from the results that when theproportion of the ethylene oxide unit is less than 15 mole%, increasingof the proportion of the unsaturated epoxide does not bring about animprovement in the cold resistance of the terpolymer rubber.

EXAMPLE 4

A vulcanizate of a terpolymer rubber composed of epichlorohydrin (60mole%), ethylene oxide (34 mole%) and allyl glycidyl ether (6 mole%) wasprepared in accordance with the compounding recipes shown in Table 6 andthe same vulcanization conditions as in Example 1, and tested for sourgasoline resistance in the same way as in Example 1. The tensile test ina normal condition was carried out in accordance with JIS K-6301. Theresults are shown in Table 7.

                  TABLE 6                                                         ______________________________________                                                       Run No.                                                                       19    20      21      22                                       ______________________________________                                        Terpolymer rubber                                                                              100     100     100   100                                    Stearic acid     1       1       1     1                                      FEF carbon black 40      40      40    40                                     Red lead         7       --      5     5                                      Magnesium oxide  --      5       --    --                                     2-Mercaptoimidazoline                                                                          1.2     --      0.3   0.3                                    Trithiocyanuric acid                                                                           --      1.0     --    --                                     Sulfur           --      --      0.8   1.6                                    1,3-Diphenyl guanidine                                                                         --      --      0.5   0.5                                    Dibenzothiazyl disulfide                                                                       --      --      1.5   1.5                                    Nickel dibutyldithiocarbamate                                                                  1       1       1     1                                      ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                                     Run No.                                                                       19     20       21      22                                                    Invention   Comparison                                           ______________________________________                                        Tensile strength, kg/cm.sup.2                                                                173      138      167   159                                    Elongation, %  230      320      260   190                                    Hardness, JIS   67       69       68    72                                    Sour gasoline resistance                                                      (1) Softening resistance                                                                     A        A        D     D                                      (2) Resistance to embrit-                                                                    No       No       --    --                                     tlement        cracking cracking                                              ______________________________________                                    

The results demonstrate that the vulcanizates obtained by vulcanizationutilizing the chlorine atom of epichlorohydrin (i.e., the vulcanizateobtained by using 2-mercaptoimidazoline or trithiocyanuric acid as avulcanizing agent) exhibited superior resistance to sour gasoline, butthat the sulfur-vulcanized products obtained by vulcanization utilizingthe unsaturated bond of allyl glycidyl ether had markedly poor sourgasoline resistance.

EXAMPLE 5

Example 1 was repeated except that a mixture of a copolymer rubberprepared from epichlorohydrin (90 mole%) and allyl glycidyl ether (10mole%) by a known solution polymerization method using an organoaluminumcompound catalyst with a copolymer rubber (CHC-1) composed ofepichlorohydrin (50 mole%) and ethylene oxide (50 mole%) was used inaccordance with each of the formulations shown in Table 8. The resultsare shown in Table 8.

                  TABLE 8                                                         ______________________________________                                                  Run No.                                                                       23   24     25     26   27   28                                               Comparison                                                                            Invention   Comparison                                      ______________________________________                                        Composition of the                                                            rubber mixture                                                                (mole %)                                                                      Epichlorohydrin                                                                           50     66     70   74   78  82                                    Ethylene oxide                                                                            50     30     25   20   15  10                                    Allyl glycidyl                                                                             0      4      5    6    7   8                                    ether                                                                         Sour gasoline                                                                 resistance                                                                    (1) Softening                                                                             D      C      A    A    A   A                                     resistance                                                                    (2) Resistance to                                                                         --     --     No cracking occurred                                embrittlement                                                                 Cold resistance                                                                           No breakage occurred                                                                            Broken                                          ______________________________________                                    

As is seen from Table 8, CHC-1 easily softens and disintegrates in sourgasoline, but its sour gasoline resistance can be improved by mixing itwith an epichlorohydrin/allyl glycidyl ether copolymer rubber. It isalso appreciated from the table that no effect is produced when theproportion of allyl glycidyl ether in the mixture is less than 5 mole%,and the rubber composition has poor cold resistance if the proportion ofethylene oxide is less than 15 mole%.

EXAMPLE 6

Example 1 was repeated except that the ratio of epichlorohydrin to allylglycidyl ether was changed to 80/20. The results are shown in Table 9.

                  TABLE 9                                                         ______________________________________                                                  Run No.                                                                       29      30    31     32  33   34                                              Compari-              Compari-                                                son     Invention     son                                           ______________________________________                                        Composition of the                                                            rubber mixture                                                                (mole %)                                                                      Epichlorohydrin                                                                           56        59    62   68  71   74                                  Ethylene oxide                                                                            40        35    30   20  15   10                                  Allyl glycidyl                                                                             4         6     8   12  14   16                                  ether                                                                         Sour gasoline                                                                 resistance                                                                    (1) Softening                                                                             D         B     A    A   A    A                                   resistance                                                                    (2) Resistance                                                                            --        No cracking   Cracking                                  to embrit-            occurred      occurred                                  tlement                                                                       Cold resistance                                                                           No breakage occurred                                                                              Broken                                        ______________________________________                                    

As is seen from Table 9, when the proportion of allyl glycidyl ether inthe rubber mixture is less than 5 mole%, the vulcanizate easily softensand disintegrates in sour gasoline. When the proportion of allylglycidyl ether exceeds 15 mole%, the vulcanizate shows good sourgasoline resistance but loses rubbery elasticity; in the embrittlementresistance test, this vulcanizate develops cracks and is defective forpractical application.

EXAMPLE 7

A copolymer rubber composed of epichlorohydrin (85 mole%) and allylglycidyl ether (15 mole%) and CHC-1 were mixed in a ratio of 40:60 sothat the rubber mixture obtained contained 64 mole% of epichlorohydrin,30 mole% of ethylene oxide and 6 mole% of allyl glycidyl ether, andvulcanized in accordance with each of the compounding recipes shown inTable 10. Each of the vulcanizates was tested in the same way as inExample 1. The results are shown in Table 11.

                  TABLE 10                                                        ______________________________________                                                       Run No.                                                                       35    36      36      37                                       ______________________________________                                        Epichlorohydrin-type rubber                                                                    100     100     100   100                                    mixture                                                                       Stearic acid     1       1       1     1                                      FEF carbon black 40      40      40    40                                     Red lead         7       --      5     5                                      Magnesium oxide  --      5       --    --                                     2-Mercaptoimidazoline                                                                          1.2     --      0.3   0.3                                    Trithiocyanuric acid                                                                           --      1.0     --    --                                     Sulfur           --      --      0.8   1.6                                    1,3-Diphenyl guanidine                                                                         --      --      0.5   0.5                                    Benzothiazyl disulfide                                                                         --      --      1.5   1.5                                    Nickel dibutyldithio-                                                                          1       1       1     1                                      carbamate                                                                     ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                                      Run No.                                                                       35    36       37      38                                                     Invention  Comparison                                           ______________________________________                                        Sour gasoline resistance                                                      (1) Softening resistance                                                                      A       A        C     C                                      (2) Resistance to                                                                             No cracking  --      --                                       embrittlement   occurred                                                      Cold resistance No breakage occurred                                          ______________________________________                                    

It is seen from Tables 9 to 11 that the vulcanizates obtained byvulcanization utilizing the chlorine atom of epichlorohydrin (i.e., thevulcanizate obtained by using 2-mercaptoimidazoline or trithiocyanuricacid as a vulcanizing agent) exhibit superior sour gasoline resistance,but that the sulfur-vulcanized products obtained by vulcanizationutilizing the unsaturated bond of allyl glycidyl ether have markedlypoor resistance to sour gasoline.

What we claim is:
 1. A combination of a vulcanized rubber product withan internal combustion engine which generates sour gasoline fromgasoline, said rubber product coming into contact with the sour gasolineand being formed from a vulcanizable rubber composition whichcomprises(1) 100 parts by weight of a rubber selected from the groupconsisting of (A) a terpolymer rubber composed of 35 to 80 mole% ofepichlorohydrin, 15 to 20 mole% of ethylene oxide and 5 to 15 mole% ofan unsaturated epoxide, and (B) a rubber mixture prepared by mixing anepichlorohydrin-ethylene oxide copolymer rubber with anepichlorohydrin-unsaturated epoxide copolymer rubber so that the mixturewill contain 35 to 80 mole% epichlorohydrin, 15 to 50 mole% of ethyleneoxide and 5 to 15 mole% of an unsaturated epoxide; (2) 0.2 to 10 partsby weight of a non-sulfur vulcanizing agent selected from the groupconsisting of 2-mercaptoimidazolines, 2-mercaptopyrimidines,trithiocyanuric acie and trithiocyanuric acid derivatives; and (3) 0 to10 parts by weight of a vulcanization aid.
 2. The combination of claim 1wherein in the rubber product the rubber component (1) is the terpolymerrubber (A).
 3. The combination of claim 1 wherein in the rubber productthe rubber component (1) is the rubber mixture (B).
 4. The combinationof claim 2 wherein in the rubber product the unsaturated epoxideconstituting the rubber (A) is selected from the group consisting ofallyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate andbutadiene monoxide.
 5. The combination of claim 3 wherein in the rubberproduct the unsaturated epoxide constituting theepichlorohydrin-unsaturated epoxide copolymer rubber in the rubbermixture (B) is selected from the group consisting of allyl glycidylether, glycidyl acrylate, glycidyl methacrylate and butadiene monoxide.6. The combination of claim 3 wherein in the rubber product theepichlorohydrin-ethylene oxide copolymer rubber in the rubber mixture(B) is composed of 30 to 70 mole% of epichlorohydrin and 70 to 30 mole%of ethylene oxide.
 7. The combination of claim 3 wherein in the rubberproduct the epichlorohydrin-unsaturated epoxide copolymer rubber in therubber mixture (B) is composed of 80 to 90 mole% of epichlorohydrin and20 to 10% of the unsaturated epoxide.
 8. The combination of claim 4wherein in the rubber product the terpolymer rubber (A) is composed of48 to 74 mole% of epichlorohydrin, 20 to 40 mole% of ethylene oxide and6 to 12 mole% of the unsaturated epoxide.
 9. The combination of claim 1wherein in the rubber product the non-sulfur vulcanizing agent isselected from the group consisting of 2-mercaptoimidazolines and2-mercaptopyrimidines.
 10. The combination of claim 1 wherein in therubber product the non-sulfur vulcanizing agent is selected from thegroup consisting of trithiocyanuric acid and its derivatives.
 11. Thecombination of claim 1 wherein in the rubber product the vulcanizationaid is present in an amount up to 10 parts by weight per 100 parts byweight of rubber and is a metal compound selected from the groupconsisting of aromatic carboxylic acid salts, saturated aliphaticcarboxylic acid salts, carbonates, phosphites, silicates and oxides ofmetal of Groups IIA, IIB and IVA of the periodic table.
 12. Thecombination of claim 1 wherein in the rubber product the non-sulfurvulcanizing agent is 2-mercaptoimidazoline and the vulcanization aid isred lead.
 13. The combination of claim 1 wherein in the rubber productthe non-sulfur vulcanizing agent is trithiocyanuric acid, and thevulcanization aid is magnesium oxide or a mixture of magnesium oxide andcalcium carbonate.
 14. The combination of claim 1 wherein the rubberproduct is a fuel system hose for said internal combustion engine. 15.The combination of claim 1 wherein the rubber product is a diaphragm forsaid internal combustion engine.
 16. The combination of claim 1 whereinthe rubber product is in the form of packing in said internal combustionengine.